Well, you'd have to do the math on manufacturing emissions vs operating emissions, factoring in remaining lifetime of the ICE vans. If they are driven enough miles EVs would come out ahead over a certain period of time.

Also, they could just buy no more new ICE vans and replace them with EVs when they get to their normal end of life.

On top of all that, you'd also have to consider that the ICE vans would be sold into the market and not destroyed.